The present invention relates generally to denial of benefits from transmitted information based on unauthorized use of a device that receives the information.
Many structures, including homes, have networks based on coaxial cable (“coax”). The networks are used for distributing video, audio, textual and any other suitable information, and any information related thereto, to network nodes in the structure. The different types of information that may be distributed may be referred to herein as “programming information.”
An organization known as The Multimedia over Coax Alliance (“MoCA™”) provides industry standards (hereinafter referred to as “MoCA”) under which the networks may be operated. MoCA™ provides at its website (www.mocalliance.org) an example of a specification which is hereby incorporated herein by reference in its entirety, for networking of digital video and entertainment information through coaxial cable. The specification has been distributed to an open membership.
Technologies available under the trademark MoCA, other specifications and related technologies (“the existing technologies”) often utilize unused bandwidth available on the coax. For example, coax has been installed in more than 70% of homes in the United States. Some homes have existing coax in one or more primary entertainment consumption locations such as family rooms, media rooms and master bedrooms. The existing technologies allow homeowners to utilize installed coax as a networking system and to deliver entertainment and information programming with high quality of service (“QoS”).
The existing technologies may provide high speed (270 mbps), high QoS, and the innate security of a shielded, wired connection combined with state of the art packet-level encryption. Coax is designed for carrying high bandwidth video. Today, it is regularly used to securely deliver millions of dollars of pay per view and premium video content on a daily basis. Networks based on the existing technologies can be used as a backbone for multiple wireless access points to extend the reach of wireless service in the structure.
Existing technologies provide throughput through the existing coaxial cables to the places where the video devices are located in a structure without affecting other service signals that may be present on the cable. The existing technologies provide a link for digital entertainment, and may act in concert with other wired and wireless networks to extend entertainment throughout the structure.
The existing technologies work with access technologies such as asymmetric digital subscriber lines (“ADSL”), very high speed digital subscriber lines (“VDSL”), and Fiber to the Home (“FTTH”), which provide signals that typically enter the structure on a twisted pair or on an optical fiber, operating in a frequency band from a few hundred kilohertz to 8.5 MHz for ADSL and 12 MHz for VDSL. As services reach such a structure via any type of digital subscriber line (“xDSL”) or FTTH, they may be routed via the existing technologies and the coax to the video devices. Cable functionalities, such as video, voice and Internet access, may be provided to the structure, via coax, by cable operators, and use coax running within the structure to reach individual cable service consuming devices in the structure. Typically, functionalities of the existing technologies run along with cable functionalities, but on different frequencies.
The programming information may be encoded using orthogonal frequency division multiplexing (“OFDM”) or any other suitable encoding scheme. The programming information may be modulated using any suitable modulation scheme, including binary phase shift keying (“BPSK”). The receivers often include bit allocation functions for allocating receiver processing bits to individual OFDM channels. The bit allocation requires an estimate of transmission noise in a signal that communicates the programming information.
Normally, a known signal, such as the Probe 1 signal (defined in the aforementioned MoCA specification) is transmitted to the receiver. The receiver generates a “transmitted” signal by demodulating the signal. The received “transmitted” signal is then, in the physical layer (“PHY”), compared to the known signal, or (in a decision-directed approach) to a “decision” based on the received “transmitted” signal. Any differences between the two signals are defined as “noise”, which may be referred to herein as “transmission noise.”
Demodulation, however, requires carrier channel estimation, whose accuracy is subject to channel noise. Channel noise introduces error into the channel estimation. The error introduces bias into the estimation of transmission noise. The bias can degrade the quality of bit allocation and can therefore degrade signal quality.
For example, the MoCA Probe1 signal payload includes BPSK data generated by a transmitter scrambler. When the same scrambler is used in the receiver, the noise can be estimated by subtracting the known signal from the estimated one, as follows:
wherein MSE is mean squared error, which is an estimate of transmission noise, x is signal magnitude, k is carrier index, n is symbol index, L is the number of symbols in a burst, w is noise samples and σw
An alternative approach to noise estimation is a data directed approach. In data directed approach, a receiver scrambler is not required. A data directed approach requires the assumption that in the received signal, the signal-to-noise ratio (“SNR”) is favorably high and that the decision is always correct.
For systems using BPSK modulation, in which only the real portion of a signal (i.e., the real portion of the mathematical model of a signal) is used in the decision,
{tilde over (x)}k(n)=sgn{Re{{circumflex over (x)}k(n)}}, (Eqn. 2)
in which {tilde over (x)}k(n) is the decision on the value of received data. When SNR is favorable, {tilde over (x)}k(n) is approximately equal to the sent data, xk(n).
In both cases described above, the estimation of the “transmitted” signal requires knowledge of the channel transfer function. Since the channel, in general, is unknown, part of the received data sequence is used for channel estimation. Channel estimation based on noisy samples has an error that induces estimation bias in both procedures described above. The bias may be shown by defining new random variable yk(n) as follows:
wherein h is a channel transfer function, v is channel noise before equalization and “*” indicates a complex conjugate.
If channel estimation does not include error, then The mean of yk(n) is zero. The variance of yk(n) is exactly the noise variance, as follows:
Equation 4 shows that the expectation of yk is the noise variance. (The expectation is therefore, in mathematical terms, “unbiased.”) The received signal, however, is accepted for analysis only after it undergoes channel estimation. Since the channel estimation is based on a noisy signal, the estimation includes error. The error may be constant over the burst. The error biases the MSE and, thus the estimate of transmission noise.
The received signal may more accurately be described by the random variable ψ, as follows:
wherein ek is error in the channel estimation for carrier channel k. Based on Eqn. 5:
E{ψk}=0, and (Eqn. 6)
E{|ψk|2}=(hkek)+(1+hkek)2σw
The estimation of the noise based on the equalized signal is thus biased and stretched. The bias and stretch may be different for each burst.
It would therefore be desirable to provide apparatus and methods for removing bias from estimates of transmission noise.
It is an object of the invention to provide apparatus and methods for removing bias from estimates of noise in a signal. Apparatus and methods for estimating channel noise, substantially as shown in and/or described in connection with at least one of the figures, and as set forth more completely in the claims, are therefore provided.
The above and other features of the present invention, its nature and various advantages will be more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, and in which:
Apparatus and methods for estimating transmission noise in a programming information signal are provided. The methods may include a method for estimating channel noise power in binary phase shift keying (“BPSK”) modulated telecommunication. Such a method may include receiving over the channel a first known signal. The first known signal may have an identified functional form. The method may include formulating a channel transfer function estimate for the channel. The channel transfer function estimate may be based on the first known signal and may include a channel estimation error. The method may include receiving over the channel a second BPSK signal. The second BPSK signal may include the programming information. The second BPSK signal may include noise. The noise may be quantified in terms of power. The method may include equalizing the second BPSK signal using the transfer function estimate. The method may include estimating the second BPSK signal noise power in such a manner that the noise power estimate is substantially independent of the channel estimation error, as described below.
In BPSK modulation, only the real portion of an equalized signal is used in the signal identification decision, so xk(n)sgn{Re{{circumflex over (x)}k(n)}}=1. A new random variable zk may be defined as follows:
The mean of zk(n) is proportional to the channel estimation error. The second moment of zk(n), which is equal to the second moment of ψk(n) (see Eqn. 7), is:
The unbiased noise estimation can be written as
When SNR is high,
To evaluate the unbiased noise estimation, as approximated by Eqn 13, the following variables may be calculated using a logic circuit, a software routine or any other suitable approach.
Illustrative features of the invention are described below with reference to
r(t)=s(t)*h(t)+w(t) (Eqn. 17)
Analog-to-digital signal converter 110 may convert r(t) to r(n), which may be a time-domain digital signal. Time-domain signal processing module 112 may perform signal acquisition, filtering, up-sampling, down-sampling or any other suitable functions. The output of time-domain signal processing module 112 may be input to fast Fourier transform module 114.
Fast Fourier transform module 114 may output a frequency-domain signal that includes encoded data. Equalizer 116 removes channel effect h(t) from the spectrum by deconvolution, inversion or any other suitable approach. Channel estimation module 118 generates frequency-dependent channel transfer function ĥk based on the spectrum from fast Fourier transform module 114. Channel estimation module 118 provides ĥk to equalizer 116 to remove channel effect h(t). Equalizer 116 transmits output {circumflex over (x)}k(n)=xk(n)+vk(n) to decision module 122 (see
Output {circumflex over (x)}k(n) is then used by decision module 122 to generate frequency-domain programming information signal {tilde over (x)}k(n). Noise estimation module 120 may use output {circumflex over (x)}k(n) from equalizer 116 and output {tilde over (x)}k(n) from decision module 122 to calculate estimate σw
Each channel may include circuitry for 2's complement conversion tables 312 and 314. Each channel may include a selector such as 316 and 318 for selection of the inverted or non-inverted bits of the real and imaginary parts of the signal. Sign bit 319 may cause preconditioning circuit 302 to select the inverted or non-inverted real and imaginary parts of zk(n) (set forth in Eqn. 14). The real and imaginary parts of zk(n) are provided at precondition circuit outputs 320 and 322, respectively.
The logic path for calculation of the real portion 330 of B (see Eqn. 16) includes output 320 of preconditioning circuit 302 and adder block 332 for adding to output 320 the constant −1 from register 334. The path then includes adder block 336 for accumulating a sum of L values of the real portion of yk(n), where L is the number of OFDM symbols in a burst.
The logic path for calculation of the imaginary portion 340 of B (see Eqn. 16) includes output 322 of preconditioning circuit 302 and adder block 342 for accumulating a sum of L values of the imaginary portion of yk(n).
The logic path for calculation of A (335), which is purely real (see Eqn. 15) includes outputs 320 and 322 of preconditioning circuit 302. The signal from output 320 is passed through adder 332 for the addition of the constant −1 from register 334. Multiplier block 334 squares the result of adder block 332 and feeds the resulting product to adder block 346. Multiplier block 348 generates a squared value of the imaginary portion of yk(n) based on output 322 of preconditioning circuit 302. The results of multiplier blocks 334 and 348 are added together in adder block 346. Adder block 350 accumulates a sum of L values of the output of adder block 346.
The values Re{B} (330), A (335) and Im{B} (340) may be stored in one or more registers. The values may be combined in accordance with Eqns. 13-16 to quantify σw
Device 400 may include single or multi-chip module 402, which can be one or more integrated circuits, and which may include logic configured to: perform mathematical operations on signals representing signal noise power or to perform any other suitable logical operations. Device 404 may include one or more of the following components: I/O circuitry 404, which may interface with coaxial cable, telephone lines, wireless devices, output devices, a keypad/display control device or any other suitable media or devices; peripheral devices 406, which may include counter timers, real-time timers, power-on reset generators or any other suitable peripheral devices; processor 408, which may control process flow; and memory 410. Components 402, 404, 406, 408 and 410 may be coupled by a system bus or other interconnections 412 and may be present on one or more circuit boards such as 420. In some embodiments, the components may be integrated into a single chip.
It will be appreciated that software components of the present invention including programs and data may, if desired, be implemented in ROM (read only memory) form, including CD-ROMs, EPROMs and EEPROMs, or may be stored in any other suitable computer-readable medium such as but not limited to discs of various kinds, cards of various kinds and RAMs. Components described herein as software may, alternatively, be implemented wholly or partly in hardware, if desired, using conventional techniques.
Thus, apparatus and methods for detecting and contravening unauthorized use of devices are therefore provided. Persons skilled in the art will appreciate that the present invention can be practiced using embodiments of the invention other than those described, which are presented for purposes of illustration rather than of limitation. The present invention is limited only by the claims that follow.
Number | Name | Date | Kind |
---|---|---|---|
3836888 | Boenke et al. | Sep 1974 | A |
4413229 | Grant | Nov 1983 | A |
4536875 | Kume et al. | Aug 1985 | A |
4608685 | Jain et al. | Aug 1986 | A |
4893326 | Duran et al. | Jan 1990 | A |
5052029 | James et al. | Sep 1991 | A |
5343240 | Yu | Aug 1994 | A |
5421030 | Baran | May 1995 | A |
5440335 | Beveridge | Aug 1995 | A |
5570355 | Dail et al. | Oct 1996 | A |
5671220 | Tonomura | Sep 1997 | A |
5796739 | Kim et al. | Aug 1998 | A |
5802173 | Hamilton-Piercy et al. | Sep 1998 | A |
5805591 | Naboulsi et al. | Sep 1998 | A |
5805806 | McArthur | Sep 1998 | A |
5815662 | Ong | Sep 1998 | A |
5822677 | Peyrovian | Oct 1998 | A |
5822678 | Evanyk | Oct 1998 | A |
5845190 | Bushue et al. | Dec 1998 | A |
5850400 | Eames et al. | Dec 1998 | A |
5854887 | Kindell et al. | Dec 1998 | A |
5856975 | Rostoker et al. | Jan 1999 | A |
5877821 | Newlin et al. | Mar 1999 | A |
5886732 | Humpleman | Mar 1999 | A |
5896556 | Moreland et al. | Apr 1999 | A |
5917624 | Wagner | Jun 1999 | A |
5930493 | Ottesen et al. | Jul 1999 | A |
5963844 | Dail | Oct 1999 | A |
5982784 | Bell | Nov 1999 | A |
6009465 | Decker et al. | Dec 1999 | A |
6028860 | Laubach et al. | Feb 2000 | A |
6055242 | Doshi et al. | Apr 2000 | A |
6069588 | O'Neill, Jr. | May 2000 | A |
6081519 | Petler | Jun 2000 | A |
6081533 | Laubach et al. | Jun 2000 | A |
6111911 | Sanderford et al. | Aug 2000 | A |
6118762 | Nomura et al. | Sep 2000 | A |
6157645 | Shobatake | Dec 2000 | A |
6167120 | Kikinis | Dec 2000 | A |
6219409 | Smith et al. | Apr 2001 | B1 |
6229818 | Bell | May 2001 | B1 |
6243413 | Beukema | Jun 2001 | B1 |
6304552 | Chapman et al. | Oct 2001 | B1 |
6307862 | Silverman | Oct 2001 | B1 |
6466651 | Dailey | Oct 2002 | B1 |
6481013 | Dinwiddie et al. | Nov 2002 | B1 |
6526070 | Bernath | Feb 2003 | B1 |
6553568 | Fijolek et al. | Apr 2003 | B1 |
6563829 | Lyles et al. | May 2003 | B1 |
6611537 | Edens et al. | Aug 2003 | B1 |
6622304 | Carhart | Sep 2003 | B1 |
6637030 | Klein | Oct 2003 | B1 |
6650624 | Quigley et al. | Nov 2003 | B1 |
6745392 | Basawapatna et al. | Jun 2004 | B1 |
6763032 | Rabenko et al. | Jul 2004 | B1 |
6816500 | Mannette et al. | Nov 2004 | B1 |
6831899 | Roy | Dec 2004 | B1 |
6862270 | Ho | Mar 2005 | B1 |
6950399 | Bushmitch et al. | Sep 2005 | B1 |
6985437 | Vogel | Jan 2006 | B1 |
6996198 | Cvetkovic | Feb 2006 | B2 |
7035270 | Moore et al. | Apr 2006 | B2 |
7065779 | Crocker et al. | Jun 2006 | B1 |
7089580 | Vogel et al. | Aug 2006 | B1 |
7116685 | Brown et al. | Oct 2006 | B2 |
7127734 | Amit | Oct 2006 | B1 |
7133697 | Judd et al. | Nov 2006 | B2 |
7146632 | Miller | Dec 2006 | B2 |
7194041 | Kadous | Mar 2007 | B2 |
7292527 | Zhou et al. | Nov 2007 | B2 |
7296083 | Barham et al. | Nov 2007 | B2 |
7327754 | Mills et al. | Feb 2008 | B2 |
7487532 | Robertson et al. | Feb 2009 | B2 |
7532693 | Narasimhan | May 2009 | B1 |
7606256 | Vitebsky et al. | Oct 2009 | B2 |
7653164 | Lin et al. | Jan 2010 | B2 |
7675970 | Nemiroff et al. | Mar 2010 | B2 |
20010039660 | Vasilevsky | Nov 2001 | A1 |
20020010562 | Schleiss et al. | Jan 2002 | A1 |
20020021465 | Moore et al. | Feb 2002 | A1 |
20020059623 | Rodriguez et al. | May 2002 | A1 |
20020059634 | Terry et al. | May 2002 | A1 |
20020069417 | Kliger | Jun 2002 | A1 |
20020078247 | Lu et al. | Jun 2002 | A1 |
20020078249 | Lu et al. | Jun 2002 | A1 |
20020097821 | Hebron et al. | Jul 2002 | A1 |
20020136231 | Leathurbury et al. | Sep 2002 | A1 |
20020141347 | Harp et al. | Oct 2002 | A1 |
20020150155 | Florentin et al. | Oct 2002 | A1 |
20020166124 | Gurantz et al. | Nov 2002 | A1 |
20020174423 | Fifield et al. | Nov 2002 | A1 |
20020194605 | Cohen et al. | Dec 2002 | A1 |
20030013453 | Lavaud et al. | Jan 2003 | A1 |
20030016751 | Vetro et al. | Jan 2003 | A1 |
20030063563 | Kowalski | Apr 2003 | A1 |
20030066082 | Kliger | Apr 2003 | A1 |
20030099253 | Kim | May 2003 | A1 |
20030152059 | Odman | Aug 2003 | A1 |
20030169769 | Ho et al. | Sep 2003 | A1 |
20030193619 | Farrand | Oct 2003 | A1 |
20030198244 | Ho et al. | Oct 2003 | A1 |
20040037366 | Crawford | Feb 2004 | A1 |
20040107445 | Amit | Jun 2004 | A1 |
20040163120 | Rabenko et al. | Aug 2004 | A1 |
20040177381 | Kliger | Sep 2004 | A1 |
20040224715 | Rosenlof et al. | Nov 2004 | A1 |
20040258062 | Narvaez | Dec 2004 | A1 |
20050115703 | Terry et al. | Jan 2005 | A1 |
20050152359 | Giesberts et al. | Jul 2005 | A1 |
20050175027 | Miller et al. | Aug 2005 | A1 |
20050204066 | Cohen et al. | Sep 2005 | A9 |
20050213405 | Stopler | Sep 2005 | A1 |
20060062250 | Payne, III | Mar 2006 | A1 |
20060078001 | Chandra et al. | Apr 2006 | A1 |
20060256799 | Eng | Nov 2006 | A1 |
20060256818 | Shvodian et al. | Nov 2006 | A1 |
20060268934 | Shimizu et al. | Nov 2006 | A1 |
20060280194 | Jang et al. | Dec 2006 | A1 |
20070025317 | Bolinth et al. | Feb 2007 | A1 |
20070127373 | Ho et al. | Jun 2007 | A1 |
20070160213 | Un et al. | Jul 2007 | A1 |
20070206551 | Moorti et al. | Sep 2007 | A1 |
20080030265 | Ido et al. | Feb 2008 | A1 |
20080037589 | Kliger | Feb 2008 | A1 |
20080117919 | Kliger | May 2008 | A1 |
20080117929 | Kliger | May 2008 | A1 |
20080130779 | Levi | Jun 2008 | A1 |
20080178229 | Kliger | Jul 2008 | A1 |
20080189431 | Hyslop et al. | Aug 2008 | A1 |
20080225832 | Kaplan et al. | Sep 2008 | A1 |
20080238016 | Chen et al. | Oct 2008 | A1 |
20080259957 | Kliger | Oct 2008 | A1 |
20080271094 | Kliger | Oct 2008 | A1 |
20080298241 | Ohana | Dec 2008 | A1 |
20090010263 | Ma et al. | Jan 2009 | A1 |
20090060015 | Beadle | Mar 2009 | A1 |
20090165070 | McMullin | Jun 2009 | A1 |
20090217325 | Kliger | Aug 2009 | A1 |
20090316589 | Shafeeu | Dec 2009 | A1 |
20100031297 | Klein | Feb 2010 | A1 |
20100158013 | Kliger | Jun 2010 | A1 |
20100158021 | Kliger | Jun 2010 | A1 |
20100158022 | Kliger | Jun 2010 | A1 |
20100238932 | Kliger | Sep 2010 | A1 |
20100246586 | Ohana | Sep 2010 | A1 |
20100254278 | Kliger | Oct 2010 | A1 |
20100254402 | Kliger | Oct 2010 | A1 |
20100284474 | Kliger | Nov 2010 | A1 |
20100290461 | Kliger | Nov 2010 | A1 |
Number | Date | Country |
---|---|---|
0 385695 | Sep 1990 | EP |
0 622926 | Nov 1994 | EP |
1501326 | Jan 2005 | EP |
WO 9827748 | Jun 1998 | WO |
WO 9831133 | Jul 1998 | WO |
WO 9935753 | Jul 1999 | WO |
WO 9946734 | Sep 1999 | WO |
WO 0031725 | Jun 2000 | WO |
WO 0055843 | Sep 2000 | WO |
WO 0180030 | Oct 2001 | WO |
WO 0219623 | Mar 2002 | WO |
Number | Date | Country | |
---|---|---|---|
20090279643 A1 | Nov 2009 | US |